Stable concentrated aqueous dispersion of pesticides and the like



United States Patent f 2,186,011 STABLE'CONCENTRATEDAQUEUSDlsrnnsIoN Y on Pnsncmns LIKE Leo I. Novak, Dayton, fOhio, iassignorfto The Commont wealth Engineeringicompany fof/Ohio, Dayton, Ohio,

a corporatonvof Ohio No Drawing. Applictionifune '18, 1954,

, Se'l'al N0. 437,"890

1 Claim. I(Cl. 167-42) invention .relates 'to compositions for use `in lthe control Vof plant pe'sts and plant diseases. More particularly, itlrlate's 't'o concentrated dispersions -or suspensions which may-befreduced with water prior to use.

It is "desirable, obviously, yfor a manufacturer to prepareand ship compositions for use in controlling pests or treating pl'art diseases Yin a, highly concentrated form,V and let the consumeradd slhcient water to the concentrate to reduce it to the concentration of the active essential 'ingredient `de'sir'e'd for application to the plant or soil. Shipment `o`f compositions comprising a high vconcentration of the active-essential ingredient and a relatively 'small atn'ountof Vwa'te'r saves shipping expense for the 'manufacturer vand this, Vin turn, may be passed on to the consumer. v A

Considerable diiclty h as been experienced in .preparing-.homogeneous spra-yble compositions by the addition of water to compositionsv comprising a high concentration of solid, water-insoluble active pesticides, Aplant hormones and Vlikefingred'ients in water .for the reason that most of the dispensing or suspending aids available for use Vin preparing the concentrates do not effectively maintain `the waterlinsoluble particles of the active jingredient in the dispersed or suspended-condition. The particles tend to `settle `or Yfcake at the bottom ofthe container in which the'concentrate is packaged, and it is dii'cult to 1re-disperse the particles inthe water added for diluting the composition to the desired concentration of the active ingredient. Those dispersing agents which may "improve the stability of the initial highly concentrate'd dispersion generally must be used `in al comparatively large amount.

lOne of the objects of the present invention is to produce highly concentrated, stable dispersions of solid, particulate pest controlling and plant treating agents.

Another object is to provide stable highly concentrated dispersions of this type containing a very small amount of a' highly effective dispersing agent.

`:Affurther .object -is to provide stable, highly concentrated dispersions ofthe active agent 'which can be reducedwith water to obtain stable, sprayable homogeneous dispersions.

These, and otherobjects and advantages which will appear hereinafter, areaccomplished by dispersing the particulate active agent in `water containing, as the dispersing aid, a very small amount of carboxymethyl dextran, which,lin accordance with the invention, has been found to be lan `extremely elfectiveadispersing agent for the vpresent purpose. Y Y

. The production of carboxymethyl dcxtranis described in the pending application ofLeo I. Novak et al., Serial No. 346,016, -led March 3l, 1953. Inbrief, the selected dextran and a c'arboxymethylating agent are reacted together -in an aqueous alkaline medium whereby the carboxym'ethyl group is substituted for vone or more hydroxyl groups in the dextran molecule. Suitable carboxymethylating agents vare chloracetic acid, `sodium chloracetate or 'chloracetam'ide vThe reaction is carried out in Van aqueous soltionof a strong `alkali metal hydroxide 'such as sodium, potassium or lithium hydroxide. Preferably, the-dextran is treated, in aqueous .solution or suspension,

with an excess of sodium or potassium chloracetate `in.

the water to dextran is between 70:1 and 120:1. The.

carboxymethyl dextran obtained `has a D. -S. (degreeof substitution `or-average number of carboxymethyl groups` per anhydroglucopyranosidic unit)vof less than 1:1 to 3:1.-

rl`he reaction results in aY viscous mass comprisingthe sodium or potassium -salt'of the carboxymethyl dextran. This viscous masscomprising the salt of Vthe ethermay be precipitated from the crude reaction mass by -alnonf solvent for the salt, as .bymeans of any water-mis'cible alcohol, e. g., methyl, ethyl, prop'yl, isopropyl ort-bu'tyl, or by means of any other organic, water-miscible solvent Which does not dissolve the salt, such as, for instance, acetone.

The `free carboxymethyl `dextran may be recovered from the salt by mixingthelatt'er with water, acidifying to atpH of about2.0, and precipitating therether by means of acetone or a water-miscible alcoholas speciedfabove. The `p'H o'f.2.0 not critical and -other acidA pH values may b'e used. However, nthe highest yields of the fr'ee ether Vhave been obtained by precipitation at pH 2.0.

The dextran which is carboxymethylated 'may be obtained in -various ways. It is usually biosynthesized from i sucrose by inoculating an'aqueous sucrose-bearing nutrient medium with a culture of a-d'extranrproducing microorganism, such as those of theLeuconostoc mesenterodes or -L. dextrancum types, or the enzyme isolated from theculture, and holding the mass until the dextran .is produced in lmaximum yield. Microorganisms which may be used include those bearing the following NRRL (Northern Regional Research Laboratory) designations: Leuconostoc mesenteroz'des B-512, B-ll9, B-'1146, B1190, B-742, -B-l 191, B-1l96, Bl208, B'l216, B1120, B-1l44, B-523; Streptobacterium dextrancum B-1254 and Betabacterum vermforme B-l139.

The native dextran present in the fermentate may be isolated by precipitation using a water-miscible aliphatic alcohol or ketonepuried, and reduced to fine powder form for carboxymethylation. This native dextran biosynthesized under the conventional conditions is normally characterized by a very high molecular weight, calculated to be in the millions. In preparing carboxymethyl ethers for use as dispersing `agent in the compositions of this invention, the native dextran of very high molecular weight may be used or, prior to carboxymethyl` ation thereof, it may be partially hydrolyzed to lower molecular weight dextran. Also, biosynthesis of the dextran may be conducted from the sucrose under special, controlled conditions such that the resulting dextran has a molecular Weight lower than that ofthe dextran produced under the conventional conditions. That ldextranmay also be used. In generaL'the dextran carboxymethylated to obtain the dispersing aid may have a molecular Weight of 5000 to ISOXlOG, determined by light scattering measurements. However, the presently preferred carboxymethyl dextran for use as dispersing agent in these compositions is the ether derived from Leuconostoc mesenterodes B-V512 native (unhydrolyzed) dextran (or from dextran equivalent to that native dextran) and containing an average of 2.0 to 3.0 carboxy- Patented Mar. 19, 1951 3 methyl groups per anhydroglucopyranosidic unit. That carboxymethyl dextran is strikingly effective in stabilizing aqueous di-spersions of the solid, particulate pest con` trolling and plant treating agents in extremely small concentrations. Amounts of the ether between 0.2% and 0.5% stabilize the dispersions most effectively and for indefinite periods of time.

The carboxymethyl dextran may be used to stabilize concentrated aqueous dispersions of all types of active plant-treating agents which are in solid particulate form.

Such agents are variously designated as insecticides or pesticides, herbicides, fungicides, miticides, arachnicides, plant hormones, growth regulators, defoliants and so on. Specific agents which, in particulate form, may constitute the active or essential ingredient of the compositions include DDT [1,1bis(pchlorophenyl) 2,2,2-trichloroethanel, phenothiazine, piperonyl butoxide, 3-(p-chloro phenyl)1,1dimethylurea, isopropyl-N-chlorophenyl carbonate, phenyl mercuric acetate, chloranil, various quinones and dithiocarbamates that are generally used as fungicides, copper salts of quinolinic acid .and quinoline, 21 chloroethyl-l-methyl-Z-(p-butylphenoxy) ethyl sulfte; p-chlorophenyl-p-chlorbenzenesulfonate; octomethyl pyrophosphoramide, -[2-ethylmercapto] ethyl-0,0diethyl thiophosphate, and halophenyl esters of halobenzene sulfonic acid.

The concentrated dispersions of the invention may be prepared by simply adding an amount of the particulate active agent between 30% and 65% by Weight of the total weight of the composition to water containing a small amount, such as between 0.1% and 0.5% by Weight, of the carboxymethyl dextran and agitating the mixture until the active agent is uniformly dispersed. 0r the active agent may be dispersed in the water with vigorous agitation and the carboxymethyl dextran added to the dispersion, the agitation being continued during such addition. The resulting product is characterized by high viscosity and may be, and generally is, a stable gel in which the particles of the active agent are maintained in a state of uniform dispersion in the aqueous phase.

The particle size of the active ingredient is not critical and very line particles as well as particles of larger size may be electively dispersed with the aid of the carboxymethyl dextran. Particles having a size ranging from l0 to 250 microns may be used.

The stabilized highly viscous dispersions or gels may be reduced with water, prior to use, to obtain dilute dispersions of comparatively low concentration with respect to the active ingredient without difiiculty and by simply adding the desired amount of water to the gel with agita^ tion.

The invention is illustrated by the following examples,Y

in which the parts are by weight unless otherwise stated. Example l Forty parts of powdered (l0 micron) 1,1-bis (p-chloro-` phenyl)-2,2,2trichloroethane, 60 parts of water and 0.5l

part of carboxymethyl dextran derived from B-512 native dextran and having a D. S. of 2.9, are Vintroduced into a vessel equipped with an agitator, and thoroughly agitated for 2 minutes. The resulting highly viscous dispersion is fed into containers for shipment or storage.

Example l1I f Fifty parts of powdered phenothiazine, 49.5 parts of water and 0.5 part of the carboxymethyl dextran of Ex.

described in Examples I and II, amounts of the carboxy-l methyl dextran of from 0.1% to 1.0% but usually not higher than 0.5% being used to effect the dispersion.'y

Dispersions may be prepared containing one or' more of thefollowing ingredients, in addition to or in place of DDT: chlorinated naphthalenes, benzene hexachloride,

I dichlorodiphenyl ethane, dparachlorophenyl methyl carbinol, trichloro-diphenyl ethane, diuoro diphenyl trichloroethane, pyrethrins, and rotenone or derris extracts.

If desired, a wetting agent may be included in the composition. used in conjunction with pestv control and plant treating compositions may be used, such as non-ionic polyethylenev` glycol monoalkyl ethers and surfactants of the type of Aerosol OT (sodium sulfosuccinate ester of a long chain fatty alcohol) may be employed.

It may also be desirable to include preservatives which function to inhibit the growth of those microorganisms which tend to flourish in aqueous dispersions, such as aromatic carboxylic acids and chlorinated phenols and cresols. Sodium orthophenyl phenate is typical of the preservatives which may be used.

`Instead of using carboxymethyl dextran as such, the salts resulting from neutralization of the carboxy groups with alkaline reagent, i. e., the fixed and volatile alkalies, to form sodium, potassium, ammonium and related amine salts of the ether may be used. Thus, the sodium or potassium salt formed as the initial productin the carboxymethylating process described herein may be used directly, without recovery of the free ether therefrom.v

However, the free ether is presently preferred.

In appropriate instances, the stable concentrated dispersions of the invention can be added to water-reducible or emulsion paints, to produce insecticidal points.

It has been observed that DDT and like pesticides exhibit toxicity to warm blooded animals when used in solutions in fatty oils, due to the assimilation of the DDT through the skin and mucous membranes when in solu-v tion in fatty solvents. The present compositions, being free of fatty solvents, avoid that problem since the activeV agents are substantially insoluble in water and only dispersed in the aqueous phase.

The concentrated dispersions or gels may be reduced with water to any appropriate concentration of the active ingredient. A final active ingredient concentration of 1% to 10% is generally useful, depending on the particular active ingredient and the purpose for which it isY used. These water-reduced dispersions may be applied in any suitable way, to the soil, directly to plants, or in a room or other enclosed space. They may be sprayed or otherwise applied on painted surfaces.

Also, in appropriate instances, and depending on the'l active ingredient, the water-reduced dispersions may be applied directly to the skin as protectives against pest attack. Dispersions of suitable active ingredients may' be used as a rinse or spray for clothing that is to be worn4 in infected and infested areas or stored, and animals can be dipped or sprayed in water-reduced dispersionsV of suitable active pest-controlling agents to rid them of ticks,

A lice, fleas, etc.

- The dispersions containing the carboxymethyl dextran are stable to heat and may be stored safely in hot climates.;

The outstanding advantage of the dispersions, -addi- A tional to the stability thereof, is the small amount of carboxymethyl dextran required to disperse the particulate active ingredient and maintain the particles in the dispersed state so that settling out thereof during shipping or storage is prevented. This stability results from` the pronounced viscosity changes in aqueous media brought about by extremely small amounts ofthe car- Those wetting agents which are commonlyv Various changes and modications in details may be made in carrying out the invention without departing from the spirit and scope thereof and, therefore, it is to be understood that it is not intended to limit the invention except as defined in the appended claim.

What is claimed is:

Concentrated pesticidal compositions consisting essentially of water, an effective amount of a substantially water-insoluble, particulative, active pesticide dispersed in the water and, as dispersant for the pesticide and thckener for the composition, from about 0.1% to 1.0% by weight of a substance selected from the group consisting of carboxymethyl dextran containing an average of about 2.0-3.0 carboxymethyl groups per anhydroglucopyranosidic unit, and alkali metal salts of said carboxy methyl dextran.

References Cited in the file of this patent UNITED STATES PATENTS Gaver Sept. 2, 1952 Coash Oc-t. 14, 1952 OTHER REFERENCES Walton: Manufacturing Chemist, August 1953, v01. 24, No. 8, p. 333.

Whistler et al.: Polysaccharide Chemistry, Academic Press, New York, 1953, p. 380. 

